GNSS techniques are used to determine one or more of position, velocity, and time (PVT) of a GNSS receiver. GNSS includes the Global Positioning System (GPS) of the United States, the GLONASS system of Russia, the GALILEO system of European Union, the BEIDOU/COMPASS system of China and any other similar satellite systems. GNSS technology has become mainstream for consumer electronics over the past few years. Products such as GPS enabled smart phones and Personal Navigation Devices (PND) are wildly popular and very affordable. As the demand for GNSS technology expands into new positioning applications, GNSS receiver designs struggle to meet the requirements that many of these applications have for low cost, very low power consumption, and extremely fast time to first fix (TTFF). These devices may need to operate in challenging environments where traditional receivers suffer degraded performance or even complete failure.
U.S. Pat. No. 7,133,772 to Global Locate Inc. discloses a method and apparatus for locating position of GPS receiver without decoding the time tag from satellite navigation data, where an accurate absolute time is obtained from a wireless communication system. Thus the system needs to be connected to the wireless communication system in order to operate. As such, the system cannot be operated autonomously.
U.S. Pat. No. 6,417,801 to Global Locate Inc. discloses a method and apparatus for computing GPS receiver position without decoding the time tag from satellite navigation data and without accurate absolute time. When operating autonomously and an a-priori estimate of position is not known, the method of “grid-search” assumes an a-priori position and tests the a-posteriori residuals from least squares to confirm if the solution is valid, repeating this process until a valid solution is found. Thus, additional processing power is needed as the least squares process is repeated. Further, as an a-posteriori residual test requires redundant measurements, the method cannot be used when there is a minimum set of measurements available.
There is a need, therefore, to provide an implementable GNSS receiver system that is operable to provide a fast, autonomous and reliable TTFF that does not require an initial position, and at the same time, reducing processing power and hardware cost.